I was searching for a way to create "n-up" PDFs (a number 'n' of PDFs per page) beyond the standard options in the Print -> Layout dialog box, so of course I turned to Google (after searching macosxhints to no avail). On a whim, I searched for "print layout OS X pdf n-up," which turned up this gem: PDF Nup Maker, a handy front end for TeX's pdfpages utility. Since I already had TeX (from an installation of the GIMP using fink), I was ready to roll!
[robg adds: The above link contains a pointer to this 'TeX on Mac OS X' page, in case you don't want to use Fink.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20040923164010910